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Title: Oxygen vacancies as a link between the grain growth and grain boundary conductivity anomalies in titanium-rich strontium titanate
Author: Tkach, Alexander
Amaral, Luís
Vilarinho, Paula M.
Senos, Ana M.R.
Keywords: Strontium titanate
Grain boundary specific area
Oxygen annealing
Impedance spectroscopy
Charge transport
Conduction mechanism
Issue Date: Jun-2018
Publisher: Elsevier
Abstract: Titanium-rich (Sr/Ti = 0.995) strontium titanate (ST) ceramics, air-sintered in a temperature range of 1400–1625 °C, were reported to possess anomalies in the grain growth and analogous anomalies in the grain boundary (GB) conductivity activation energy. However, these two interface-related phenomena, occurring at GBs, could not be associated with each other using a simple “brick-layer” model. In this work we revise the topic and advocate that the deviation from the model comes from the oxygen vacancies localized at GBs of the rapidly-cooled ST ceramics. To verify this, we annealed the ceramics in oxygen and performed their systematic and comparative analysis using impedance spectroscopy. A levelling-off in the GB conductivity activation energy, which increases for ≤1.24 eV, and a four-fold decrease in the GB permittivity are observed after annealing. Thus, we confirm a key role of oxygen vacancies in relation between the grain growth and GB conductivity anomalies of as-sintered Ti-rich ST ceramics.
Peer review: yes
DOI: 10.1016/j.jeurceramsoc.2018.01.014
ISSN: 0955-2219
Appears in Collections:CICECO - Artigos
DEMaC - Artigos

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